This book is a tutorial in the “Teach Yourself… in 21 Days” style, aimed at helping readers learn the Perl programming language over a structured 21-day sequence (i.e., 21 chapters or “days”). Introduces basic Perl syntax, scalar and list data, control structures, arrays and hashes, references, regular expressions, modules and object-oriented Perl, file and directory manipulation, CGI scripting and operating system integration. Includes longer working examples rather than only fragments; each chapter includes two to three smaller examples and one major one that builds on prior concepts. Is written for beginning to intermediate programmers who wish to learn Perl quickly and thoroughly, including object-oriented Perl and modular code design.